The present invention relates to autosamplers, which are mechanical device., that can be used to extract samples from specimens, prepare the samples for analysis, and provide the samples to an analytical instrument. More particularly, the present invention relates to a needle for use with a sampling station of an autosampler to facilitate performing the above-described tasks.
Autosamplers are generally used to extract gas and liquid samples from specimens stored in containers such as vials. Once extracted, the sample can be transferred to an analytical instrument for analysis, such as the 3100 Concentrator sold by Tekmar-Dohrmann, Cincinnati, Ohio, U.S.A.
Autosamplers typically use separate sampling stations for extracting liquid and gas samples. One example of such an autosampler is described in U.S. Pat. No. 5,948,360 to Rao et al. and assigned to Tekmar Company, Cincinnati, Ohio, U.S.A. Liquid sampling typically involves extracting a known quantity of liquid from the vial that is presented to the sampling station of the autosampler, adding a standard to the sample, and transferring the sample and the standard to an analytical device. Under certain situations, the specimen must be diluted by a technician by injecting the specimen with a specified volume of methanol or a water-based solution prior to sampling. The extracted sample or methanol extract is then diluted with water prior to analysis by the analytical device.
Gas headspace extraction generally involves injecting the specimen with a solvent, such as water, agitating the specimen, and purging the specimen with a gas. Some autosamplers are adapted to perform static headspace extraction while others are adapted to perform dynamic headspace extraction. In static headspace extraction, the specimen is purged from above the specimen and the headspace is removed and transferred to the analytical device. In dynamic headspace extraction, the specimen is purged from underneath the specimen and the head space is removed and transferred to the analytical instrument. Autosamplers that are capable of performing the above sample extraction procedures include the Precept II and the 7000 HT autosamplers sold by Tekmar-Dohrmann, Cincinnati, Ohio, U.S.A.
The processes of extracting liquid and gas samples using current sampling stations require a technician to perform the standard injections, the methanol dilutions, and other process steps. As a result, in addition to being time consuming, these procedures carry the likelihood of inconsistent injections and a high potential for error. With gas extraction, such as that used for soil analysis, the vial must remain sealed to comply with EPA method 5035. Further time is lost due to the inability to perform both liquid and gas extractions at a single sampling station or autosampler station.
Therefore, a need exists for a sampling station of an autosampler that is capable of performing both liquid and gas extractions while reducing the reliance upon sample preparation by a technician, and remaining compliant with EPA method 5035. A need also exists for a needle that can facilitate the various extractions and dilutions that can be performed by such a sampling station.
A three stage needle for use with a sampling station of an autosampler is provided and is adapted to facilitate gas and liquid extractions and injections. The needle includes a bottom stage, a middle stage, and a top stage. Each of the stages of the needle includes at least one aperture used to extract gas or liquid from a specimen or perform an injection. In addition, each of the stages can be placed in fluidic communication with the sampling station to facilitate the desired extraction or injection.